Feature: Add TcpTransportExecutor to send DNS queries over TCP/IP connection,
add SelectiveTransportExecutor to retry with TCP if UDP is truncated and
automatically select transport protocol when no explicit udp:// or tcp:// scheme is given in Factory.
(#145, #146, #147 and #148 by @clue)

Feature: Support escaping literal dots and special characters in domain names.
(#144 by @clue)